Conventional apparatus exist for sensing the angular displacement, or turn of an object. These apparatus may detect changes in angular displacements of an object and provide outputs that may be used to determine such indications as location, heading, rotational speed, among others. These indications may be particularly useful when the object is a vehicle and where the operator needs to know the location and/or heading of the vehicle. A gyroscope is one such conventional apparatus used for sensing turn of an object.
A gyroscope typically includes a rotating object mounted within an enclosure, wherein the object rotates in a reference axis at a high rate of speed. The object is generally mounted on a complicated set of bearings so that when the enclosure moves, no net torque acts to change the objects' direction of angular momentum. However, these changes in angular momentum are sensed by the gyroscope. The rotating object generally must rotate at high speeds for certain mathematical assumptions to accurately describe the object's motion. When the gyroscope is mounted to an object, the gyroscope detects changes of angular momentum which may be used to determine changes in angular displacement. Angular momentum is proportional to angular velocity, and thus angular displacement may be determined from angular velocity generally through an integration calculation.
As discussed above, a gyroscopic apparatus may be used to detect changes in the angular rate of movement of an object. A typical gyroscopic apparatus used for this purpose generally includes a disk that rotates at high speed, e.g. from a few thousand rpm to upwards of 20,000 rpm. The disk may be flexible or include flexible members that extend from an axis of rotation of the gyroscope.
As the disk is rotated, any movement about an axis perpendicular to the axis of rotation of the disk will cause the flexible disk members to flex toward and away from a plurality of plate members, changing a capacitance between the plate members and the flexible disc members. An electrical circuit is provided to generate a signal based on the changing capacitance. This signal is used to determine the movement of the object about a reference axis. The signals are generally interpreted by a system which provides indications or performs corrective actions relating to the angular movement of the object. For example, one such system may provide a heading indication onboard a vehicle, the heading indication being used for navigational purposes. One such angular rate gyroscope is disclosed in U.S. Pat. No. 4,811,613 issued Mar. 14, 1989 to Phillips et al.
Drawbacks of conventional gyroscopic sensors include a susceptibility to frequent failures of the moving parts, particularly the motor that rotates the disk at high speed. The mean time between failures (MTBF) of conventional gyroscopic sensors is directly related to the number of rotations of the motor. Because frequent failures occur, the gyroscopic sensors must be frequently serviced and calibrated. Conventional sensors are also sensitive to vibration and gravity. Further, these sensors generate electrical noise because of the frequency of motor rotation.